/*
 * Lazy Load - jQuery plugin for lazy loading images
 *
 * Copyright (c) 2007-2012 Mika Tuupola
 *
 * Licensed under the MIT license:
 *   http://www.opensource.org/licenses/mit-license.php
 *
 * Project home:
 *   http://www.appelsiini.net/projects/lazyload
 *
 * Version:  1.7.2
 *
 */

// lazyload.js 不支持 jquery-1.3.2

FX.getFrame('jquery-1.5.1', function(jQuery){
    (function($, window) {

        var $window = $(window);
        // 用getGroupScrollTop/Left函数代替原有的$.offset().top/left, 因为某些img可能是unvisible的, 此时可以用相同group的值替代, 参见 fx/switch.js
        var getGroupScrollTop = function(obj){
            if ($.data(obj, "zarkfx.lazyload.scrollTop")){
                return $.data(obj, "zarkfx.lazyload.scrollTop")();
            }else{
                return $(obj).offset().top;
            };
        };
        var getGroupScrollLeft = function(obj){
            if ($.data(obj, "zarkfx.lazyload.scrollLeft")){
                return $.data(obj, "zarkfx.lazyload.scrollLeft")();
            }else{
                return $(obj).offset().left;
            };
        };

        $.fn.lazyload = function(options) {
            var elements = this;
            var settings = {
                threshold       : 0,
                failure_limit   : 0,
                event           : "scroll",
                effect          : "show",
                container       : window,
                data_attribute  : "original",
                skip_invisible  : true,
                appear          : null,
                load            : null
            };

            function update() {
                var counter = 0;
          
                elements.each(function() {
                    var $this = $(this);
                    if (settings.skip_invisible && !$this.is(":visible")) {
                        return;
                    }
                    if ($.abovethetop(this, settings) ||
                        $.leftofbegin(this, settings)) {
                            /* Nothing. */
                    } else if (!$.belowthefold(this, settings) &&
                        !$.rightoffold(this, settings)) {
                            $this.trigger("appear");
                    } else {
                        if (++counter > settings.failure_limit) {
                            return false;
                        }
                    }
                });

            }

            if(options) {
                /* Maintain BC for a couple of versions. */
                if (undefined !== options.failurelimit) {
                    options.failure_limit = options.failurelimit; 
                    delete options.failurelimit;
                }
                if (undefined !== options.effectspeed) {
                    options.effect_speed = options.effectspeed; 
                    delete options.effectspeed;
                }

                $.extend(settings, options);
            }

            /* Cache container as jQuery as object. */
            $container = (settings.container === undefined ||
                          settings.container === window) ? $window : $(settings.container);

            /* Fire one scroll event per scroll. Not one scroll event per image. */
            if (0 === settings.event.indexOf("scroll")) {
                $container.bind(settings.event, function(event) {
                    return update();
                });
            }

            this.each(function() {
                var self = this;
                var $self = $(self);

                self.loaded = false;

                /* When appear is triggered load original image. */
                $self.one("appear", function() {
                    if (!this.loaded) {
                        if (settings.appear) {
                            var elements_left = elements.length;
                            settings.appear.call(self, elements_left, settings);
                        }
                        $("<img />")
                            .bind("load", function() {
                                $self
                                    .hide()
                                    .attr("src", $self.data(settings.data_attribute))
                                    [settings.effect](settings.effect_speed);
                                self.loaded = true;

                                /* Remove image from array so it is not looped next time. */
                                var temp = $.grep(elements, function(element) {
                                    return !element.loaded;
                                });
                                elements = $(temp);

                                if (settings.load) {
                                    var elements_left = elements.length;
                                    settings.load.call(self, elements_left, settings);
                                }
                            })
                            .attr("src", $self.data(settings.data_attribute));
                    }
                });

                /* When wanted event is triggered load original image */
                /* by triggering appear.                              */
                if (0 !== settings.event.indexOf("scroll")) {
                    $self.bind(settings.event, function(event) {
                        if (!self.loaded) {
                            $self.trigger("appear");
                        }
                    });
                }
            });

            /* Check if something appears when window is resized. */
            $window.bind("resize", function(event) {
                update();
            });

            /* Force initial check if images should appear. */
            update();
            
            return this;
        };

        /* Convenience methods in jQuery namespace.           */
        /* Use as  $.belowthefold(element, {threshold : 100, container : window}) */

        $.belowthefold = function(element, settings) {
            var fold;
            
            if (settings.container === undefined || settings.container === window) {
                fold = $window.height() + $window.scrollTop();
            } else {
                fold = $container.offset().top + $container.height();
            }

            //return fold <= $(element).offset().top - settings.threshold;
            return fold <= getGroupScrollTop($(element)[0]) - settings.threshold;
        };
        
        $.rightoffold = function(element, settings) {
            var fold;

            if (settings.container === undefined || settings.container === window) {
                fold = $window.width() + $window.scrollLeft();
            } else {
                fold = $container.offset().left + $container.width();
            }

            //return fold <= $(element).offset().left - settings.threshold;
            return fold <= getGroupScrollLeft($(element)[0]) - settings.threshold;
        };
            
        $.abovethetop = function(element, settings) {
            var fold;
            
            if (settings.container === undefined || settings.container === window) {
                fold = $window.scrollTop();
            } else {
                fold = $container.offset().top;
            }

            //return fold >= $(element).offset().top + settings.threshold  + $(element).height();
            return fold >= getGroupScrollTop($(element)[0]) + settings.threshold  + $(element).height();
        };
        
        $.leftofbegin = function(element, settings) {
            var fold;
            
            if (settings.container === undefined || settings.container === window) {
                fold = $window.scrollLeft();
            } else {
                fold = $container.offset().left;
            }

            //return fold >= $(element).offset().left + settings.threshold + $(element).width();
            return fold >= getGroupScrollLeft($(element)[0]) + settings.threshold + $(element).width();
        };

        $.inviewport = function(element, settings) {
             return !$.rightofscreen(element, settings) && !$.leftofscreen(element, settings) && 
                    !$.belowthefold(element, settings) && !$.abovethetop(element, settings);
        };

        /* Custom selectors for your convenience.   */
        /* Use as $("img:below-the-fold").something() */

        $.extend($.expr[':'], {
            "below-the-fold" : function(a) { return $.belowthefold(a, {threshold : 0, container: window}); },
            "above-the-top"  : function(a) { return !$.belowthefold(a, {threshold : 0, container: window}); },
            "right-of-screen": function(a) { return $.rightoffold(a, {threshold : 0, container: window}); },
            "left-of-screen" : function(a) { return !$.rightoffold(a, {threshold : 0, container: window}); },
            "in-viewport"    : function(a) { return !$.inviewport(a, {threshold : 0, container: window}); },
            /* Maintain BC for couple of versions. */
            "above-the-fold" : function(a) { return !$.belowthefold(a, {threshold : 0, container: window}); },
            "right-of-fold"  : function(a) { return $.rightoffold(a, {threshold : 0, container: window}); },
            "left-of-fold"   : function(a) { return !$.rightoffold(a, {threshold : 0, container: window}); }
        });

    })(jQuery, window);
});

